1. Field of Invention
The invention relates to a micro crystal fiber laser and, in particular, to a micro crystal fiber laser for color lasers, a micro crystal fiber laser array, and a method of fabricating a frequency-doubling crystal fiber.
2. Related Art
Laser beams are characteristic in their high power density, highly monochromic color, high orientability, and high correlation. Therefore, they are widely used in various fields such as medical therapy, communications, information technology, and industries. Among the laser devices for generating laser beams, semiconductor lasers have the advantages of small volumes, long life cycles, cheap prices, and being suitable for mass production, in comparison with other types of laser devices (e.g. gas lasers and solid state lasers). Thus, they can be commercialized. However, in the three primitive colors (red, green, and blue) of visible light, only red semiconductor lasers can be made commercially popular. Semiconductor lasers in the blue and green bands are restricted by the problems of high prices, difficult production processes, and low light emission rate of wide energy gap semiconductor materials. Therefore, their commercialization still requires further researches and improvement.
As a result, diode-pumped solid state lasers (DPSSL) have been developed. They use semiconductor lasers whose central wavelength is in the absorption spectrum of solid state laser crystals as the stimulating light source of solid state lasers. The stimulated light is usually high power infrared light (wavelength being mostly 800 or 880 nm). The base frequency laser beam emitted by the DPSSL (infrared light with a wavelength of about 1 μm) is doubled in its frequency by the nonlinear crystal inside the resonance cavity, generating the required frequency-doubling laser beam. The DPSSL formed using this method has a better beam output mode, wide wavelength ranges, and large peak values or average power. Therefore, it is an ideal light source. However, the solid state laser crystal used as the gain medium and frequency-doubling crystal in the DPSSL is mostly an insulating material. Its thermal conductivity is worse than metals. In the horizontal excitation modes, the heat dissipation problem is especially serious, affecting the laser output efficiency. To solve this problem, a large heat dissipation system is often required. Moreover, the growth of the solid state laser crystal is very time-consuming, inevitably increasing the device price. Consequently, the current development of DPSSL is seriously restricted by the cost and heat dissipation.